Process of vulcanization.



PATENTED JULY 18 1905.

A. L. GOMSTOGK. PROCESS OF VULGANIZATION.

APPLICATION FILED DEO.19, 1903- fnventor M W,

M6522 e s ses:

morneys.

my. lmmnmmmu "mat No. 795,026. Patented July 18, 1905.

UNITED STATES PATENT OFFICE.

ALLEN L. COMSTOCK, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO BOSTOl\ RUBBER SHOE COMPANY. OF BOSTON, MASSACHUSETTS, A CORPORA- TION OF MASSACHUSETTS.

PROCESS OF VULOANYIZATION.

SPECIFICATION forming part of Letters Patent No. 795,026, dated July 18, 1905.

Application filed December 19, 1903. Serial No. 185,839.

To all whom it may concern: sure during vulcanization, thus permitting Be it known that I, ALLEN L. CoMs'roox, a the necessary heat to be applied more quickly. citizen of the United States, residing at Bos- Pressure may be applied to the air within the 50 ton, in the county of Suffolk, State of Massaheater by means of a pump, or the pressure 5 chusetts, have invented a certain new and may be obtained by the employment of ceruseful Improvement in Processes of Vulcanitain chemicals which are put into the heater zation, of which the following is a specificain the form of a salt-for example, before the tion, reference being had therein to the acprocess of vulcanization begins and which 55 companying drawing. by means of the heat applied to vulcanize My invention has for its object an imthe articles is decomposed, forming a gas provement in process of vulcanization of rubwhich operates to put the articles which are ber and allied gums. being vulcanized under a degree of pressure The invention is fully set forth in the fol which varies in proportion with the quantity 6o lowing description, and the novel features of the gas liberated. It has also been prothereof are pointed out and clearly defined posed to vulcanize in an atmosphere of a nonin the claims at the close of this specification. oxidizing or inert gas-such, for example, as

The accompanying drawing shows one carbon dioxid either in the presence of form of apparatus by the employment of pressure or without any additional pressure 65 which my process may be practiced. other than that which may result from the In vulcanizing by the usual dry-heat procexpansion of the gas by heat. This latter ess commonly employed the articles to be method while effective increases the cost of vulcanized are placed in an oven or heater vulcanization because of the cost of the nonwhich is provided with suitable heating oxidizing gas which is employed. 70 means for raising the temperature within the By the employment of my process herein- 2 5 oven to the required degree of heat. The after set forth I am enabled to obtain the articles are placed within the oven and are substantial advantages resulting from vulenveloped in an atmosphere of air while they canization in a surrounding or enveloping are being vulcanized. As the heatis applied atmosphere of non-oxidizing or inert gas un- 7 5 any vapor which may exist in the rubber or der pressure while at the same time reducing compound of which the articles are comthe cost of such vulcanization.

posed, is formed into vapor, and there are In practicing my process I employ a heater also formed or liberated in the rubber, or or oven, (shown in the drawing at A,) which composition, certain gases as the heating promay be constructed in any well-known man- 80 ceeds. This vapor or the gases which are nerto enable ittowithstand internal pressure.

3 5 liberated frequently form what are termed The oven A is provided with means by which blisters on the surface of the article, unthe temperature within the oven may be less great care is taken in the application of raised as desired. In the drawing I have heat, especially about the time when the shown the oven as jacketed at B, the jacket 8 5 temperature reaches the boiling-point of being entered by a steam-inlet pipe C and water and the melting-point of sulfur. This having a drip at D. By this means steam dry-heat process requires a considerable may be used in heating the oven but any length of time-usually from six to eight well-known means for heating the oven may, hoursand great care in racticing it. To however, be employed. 9o simplify the process of vu canization and to The oven is provided with an inlet-pipe E,

reduce the time required, it has been prowhich leads from a tank M or other source of posed to obviate the blistering of the articles supply of a non-oxidizing or inert gassuch, being vulcanized by subjecting them to presfor example, as carbon dioxid-which is under pressure. The said inlet-pipe E is pro vided with a cock F, by means of which the nonoxidizing gas under pressure in the tank may be admitted to the heating chamber or oven A. The inlet-pipe E is also connected with a pipe G, the other end of which is contained under pressure, into the heater A until the gage J on the heater indicates a pressure of fifteen pounds to the square inch. The cock F is then closed and the cock K opened, and by means of the air-pump air is umped into the heater A until the gage in icates a pressure of thirty pounds. The atmosphere within the heater will then-consist substantially of one-half non-oxidizing gas and onehalf air under a pressure of thirty pounds to the square inch. While the heater is thus being provided with the proper atmosphere, heat may be applied, (or the application of heat may be delayed until the proper atmosphere under the required pressure has been obtained,) and the heat may be raised quickly to a proper vulcanizing temperature-say 270 Fahrenheit. It is important that the re uired pressure be on the heater before the rise in temperature is such as to cause the formation of vapor or steam or the liberation of gas, since otherwise blisters might result on the surfaces of the rubber articles. The articles are allowed to remain under these conditions of heat and pressure for a suflicient length of time, usually from one to two hours, depending somewhat upon the character of the articles being treated, until they are properly vulcanized. The pressure is then removed, a cook or valve P being provided for this purpose, and the vulcanizer or heater opened and the articles removed.

I have found that articles vulcanized in the manner h'ereinabove described are of largely increased value as compared with articles which are vulcanized in an atmosphere of air, and I believe them to be substantially as valuable as, if not more valuable than, articles which are vulcanized in an atmosphere consisting Wholly of the non oxidizing gas. I do not intend herein to limit myself to the proportions named of nonoxidizing gas and air or to the specific pressures andtemperatures named, as these may be varied within certain well-known limits.

I have found that a substantial admixture of non-oxidizing gas with air is very advantageousas a vulcanizing atmosphere and that the pressures, temperatures, and times require substantial variations, according to circumstances.

The essential of my process is the employment of an atmosphere made up of a substantial proportion of non-oxidizing gas mixed with air and maintained during vulcanization under pressure. This atmosphere I do not find possible to obtain by decomposition of a salt or other chemical, as such an atmosphere contains other ingredients. My best results have been obtained by using commercially pure carbonicacid gas, which is allowed to pass from a tank containing it under pressure into the heater or oven and is then .lollowed by the admission of air into the heater or oven, a sufficient amount of the latter being forced into the heater or oven until the pressure within the same has reached thirty pounds or thereabout, or the air may be first admitted to the heater to be followed after a certain pressure has been. reached say fifteen pounds to the square inchby the gas. The presence of a substantial proportion of non-oxidizing gas in the heater 0perates presumably to prevent oxidation of the rubber, and hence to improve the product. The air in the admixture has, I believe, no deleterious effect, while serving to economically obtain the pressure necessary to prevent blistering.

What I claim is 1. The process ofvulcanizing rubber or allied gums which consists in heating the articles to be vulcanized in the presence of a surrounding atmosphere under pressure, said atmosphere consisting of a mixture of non,- oxidizing gas and air, substantially as de scribed.

2. The process of vulcanizing rubber or allied gums which consists in heating the articles to be vulcanized in the presence of a surrounding atmosphere under pressure, said atmosphere consisting of a mixture of nonoxidizing gas and. air in substantially equal proportions, substantially as described.

3. The process of vulcanizing rubber or allied gums which consists in surrounding the articles to be vulcanized by an atmosphere of non-oxidizing gas under pressure, raising the same to a substantially higher pressure by the admission of air under pressure thereby producing an admixture of air and the non-oxidizing gas, and heatin the articles to be vulcanized in the said admixture, substantially as described. p

4. The process of vulcanizing rubber or allied gums which consists in surrounding the articles to be vulcanized by an atmosphere consisting of an admixture of non oxidizing gas and air under pressure, and

In testimony whereof I am); my signature applying the necessary heat thereto, said adin presence of two Witnesses.

mixture being obtained by first admitting one of the ingredients to the heater under pressure and then forcing into the heater the otheringredient until the required pressure is obtained, substantially as described.

ALLEN L. COMSTOCK. 

